Apparatus for assembling a multiple element type electron gun structure

ABSTRACT

APPARATUS FOR ASSEMBLING A MULTIPLE ELEMENT TYPE ELECTRON GUN STRUCTURE EACH OF THE ELECTRON GUN UNITS COMPRISING FIRST TO FIFTH GRID ELECTRODES ARRANGED IN SUCCESSION ALONG THE PATH OF TRAVEL OF AN ELECTRON BEAM EMITTED FROM A CATHODIE ELECTRODE, OPPOSING ENDS OF THE THIRD AND FIFTH GRID ELECTRODES HAVING PROJECTIONS WITH A DIAMETER SMALLER THAN THE INNER DIAMETER OF THE FOURTH GRID ELECTRODE WHICH PARIALLY RECEIVES THE PROJECTIONS. THE ASSEMBLING APPARATUS INCLUDES SLOTTED SPACERS ENGAGING THE PROJECTIONS AND OTHER ELECTRODES TO ALIGN THE VARIOUS DLECTRODES. A CENTRE ROD, VARIOUYS HOLDERS AND MENS TO APPLY A LONGITUDINAL COMPRESSIVE FORCE ARE PROVIDED TO INSURE ACCURATE ALIGNMENT AND INTIMATE CONTACT OF THE GUN ELEMENTS DURING THE BONDING OPERATION.

10, 1971 SHINICHI SAWAGATA ET AL 3,598,557

APPARATUS FOR ASSEMBLING A MULTIPLE ELEMENT TYPE ELECTRON GUN STRUCTURE Filed April 21, 1969 I 6 Sheets-Sheet 1 FIG. 'I'

10 2 16a i9o 13a Z 920 0 @1415 PLATE VOLTAGE I2 fit? l-IO 0|- 1 2ND 3RD 4-ITH 51 'H CATHODEGRID GRID GRID GRID DISTANCE FROM CATHODE g 1971 SHINICHI SAWAGATA ETAL 3,5

APPARATUS FOR ASSEMBLJING A MULTIPLE ELEMENT TYPE.

1 ELECTRON GUN STRUCTURE I Filed April 21; 1969 6 Sheets-Sheet 2 A iomm 25m A1 .6 $5230 G W m D O M VOLTAGE RATIO F l G. 5

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I. m r!! Aug. 10, 1971 SH|N|CH| SAWAGATA ETAL 3,598,557

APPARATUS FOR ASSEMBLING A MULTIPLE ELEMENT TYPE ELECTRON GUN STRUCTURE Filed April 21, 1969 6 Sheets-Sheet 5 Aug. 10, 1971 SHINICHI SAWAGATA ETAL 3,598,557

APPARATUS FOR ASSEMBLING A MULTIPLE ELEMENT TYPE- ELECTRON GUN STRUCTURE Filed April 21, 1969 T 6 Sheets-Sheet 4 FIG. 11A FIG. 13

10, 1971 SHINICHI SAWAGATA ErAL 3,5

APPARATUS FOR ASSEMBLING A MULTIPLE ELEMENT TYPE ELECTRON GUN STRUCTURE Filed April 21, 1969 6 Sheets-Sheet 5 PIC-3.14

u LT! g- 1971 SHINICHI SAWAGATA ETAL 3,5

APPARATUS FOR ASSEMBLING A MULTIPLE ELEMENT TYPE ELECTRON GUN STRUCTURE Filed April 21, 1969 6, Sheets-Sheet 6 EV/IIIA 7 United States Patent 3,598,557 APPARATUS FOR ASSEMBLING A MULTIPLE ELEMENT TYPE ELECTRON GUN STRUCTURE Shinichi Sawagata, Tokyo, Masakatsu Nakahara, Yokohama-shi, and Mikio Noguchi, Hyogo-ken, Japan, assignors to Tokyo Shiboura Electric Co., Ltd., Kawasaki-shi, Japan Filed Apr. 21, 1969, Ser. No. 818,009 Claims priority, application Japan, Apr. 25, 1968, 43/27,326; July 5, 1968, 43/46,524; Sept. 30, 1968, 43/70,598

Int. Cl. C03b 23/14 US. Cl. 65-155 8 Claims ABSTRACT OF THE DISCLOSURE Apparatus for assembling a multiple element type electron gun structure each of the electron gun units comprising first to fifth grid electrodes arranged in succession along the path of travel of an electron beam emitted from a cathode electrode, opposing ends of the third and fifth grid electrodes having projections with a diameter smaller than the inner diameter of the fourth grid electrode which partially receives the projections. The assembling apparatus includes slotted spacers engaging the projections and other electrodes to align the various electrodes. A centre rod, various holders and means to apply a longitudinal compressive force are provided to insure accurate alignment and intimate contact of the gun elements during the bonding operation.

This invention relates to an apparatus for assembling a multiple element type electron gun structure.

In the conventional cathode ray tube utilised in colour television receivers, two types of electronic lenses for focussing an electron beam, ordinarily of the bipotential type and unipotential type, are incorporated into the electron gun thereof. More particularly, in the bipotential type electron gun there are provided first to fourth control grids, and an electron beam emitted from a cathode electrode is passed through a first and a second control grid, and projected upon a fluorescent screen after being focussed by a bipotential type electronic lens comprised of third and fourth grids having difierent potentials. High potentials of 4 kv. and 20 kv. for example, are applied to the third and fourth control grids, respectively.

In the high potential focussing bipotential type electron gun of the construction as above outlined there is a socalled blooming characteristic wherein the diameter of the electron beam tends to increase as the beam current increases. Thus, an increase in the brightness of the screen results in a decrease in the sharpness of a received image. There is also the problem that as the ratio of two different focussing voltages impressed upon the third and fourth grid electrodes varies, the focussing action of the electronic lens also varies greatly. To compensate for this tendency, it is necessary to provide a voltage regulator to prevent voltage variations, thus complicating the construction.

On the other hand, a unipotential type electron gun is provided with a first to fifth grid electrodes which are arranged such that an electron beam emitted from a cathode electrode is passed through the first and second grid electrodes and projected upon a fluorescent screen after being focussed by an electronic lens formed by the third, fourth and fifth grid electrodes. A voltage of 20 kv., for example, is impressed upon the third and fifth grid electrodes, whereas a voltage of zero volts is impressed upon the fourth grid electrode.

With the unipotential type electron gun of the construction abope described, the difference between potentials "ice applied to the third and fifth grid electrodes and to the fourth grid electrode is so large that it is necessary to pay particular attention to the insulation between various grid electrodes. Further, in the prior unipotential type electron gun, the third to fifth grid electrodes take the form of cylindrical electrodes having substantially the same inner diameter and are disposed on a straight line along the direction of travel of the electron beam, with a predetermined spacing therebetween. Thus, an external field may enter into the electronic lens system through gaps between these electrodes to disturb the internal lens field, with the result that clear images are not obtained.

Accordingly, the principal object of this invention is to provide an apparatus for assembling with high precision a multiple element type electron gun structure which can effectively eliminate the elfect of an external field upon an electronic lens, provides clear images, and which is of simple construction for easy fabrication.

SUMMARY OF THE INVENTION According to this invention, one type of apparatus for assembling a multiple element type electron gun structure each of the gun units including first to fifth grid electrodes which are arranged in succession along the direction of travel of an electron beam emitted from a cathode electrode, the opposing ends of the third and fifth electrodes having diameters smaller than the inner diameter of the cylindrical fourth grid electrode so that the projections are at least partially received in the fourth grid electrode comprises slotted spacers engaging the projections and other electrodes to align the various electrodes. A centre rod, various holders and means to apply a longitudinal compressive force are provided to insure accurate alignment and intimate contact of the gun elements during the bonding operation.

This invention can be more fully understood from the following detailed description when taken in connection with the accompanying drawings, in which:

FIG. 1 shows a side view, partly in section, of one embodiment of a multiple element type electron gun structure;

FIG. 2 shows a cross section of the electron gun structure taken along a line IIII and viewed in the direction of arrows shown in FIG. 1;

FIG. 3 is a graph to show a potential distribution along the axis of each electrode of the respective electron gun units shown in FIG. 1;

FIG. 4 shows curves representing the beam modulation characteristics of a conventional bipotential type electron gun and the electron gun according to the principles of FIG. 1;

FIG. 5 is a side elevational view, partly in section, of a modification of the multiple element type electron gun structure;

FIG. 6 shows a cross section of the electron gun struc ture taken along a line VIVI and viewed in the direction of arrows in FIG. 5;

FIG. 7 shows a side view, partly in section, of an apparatus according to the present invention for assembling the multiple element type electron gun structure shown in FIG. 1;

FIG. 8 is a perspective view of a pillar shaped supporting member utilised in the apparatus shown in FIG. 7;

FIGS. 9A, 9B, 10A, 10B, 11A and 11B are perspective views of first and second spacers utilised in the assembling apparatus shown in FIG. 7;

FIG. 12 is an enlarged sectional view of a portion of FIG. 7 illustrating the manner of supporting electrodes by means of spacers;

FIG. 13 is a sectional view taken along a line XIII- XIII in FIG. 12;

FIG. 14 shows a longitudinal section of a portion of the apparatus shown in FIG.

FIG. 15 is a side view, partly in section, of a portion of the apparatus shown in FIG. 14;

FIG. 16 is a perspective view of a portion of the apparatus shown in FIG. 14; and

FIG. 17 is a sectional view of a portion of a modification of the assembling apparatus.

Referring now to the accompanying drawings, FIGS. 1 and 2 show the application of this invention to a three electron gun structure utilised in shadow mask type colour television receiving tubes. The three electron gun structure comprises three independent electron gun units 1a, 1b and 1c, which are arranged to form an integral structure by means of supporting glass rods 4a, 4b and 4c and supporting bands 3 which are welded to the outer Walls of respective electrodes such that axes 2a, 2b and 20 along which respective electron beams travel constitute portions of edges of an imaginary equilateral trigonal piramid, the axis 2b being not shown. As a consequence, electron beams emitted by the respective electron gun units 1a, 1b and will intersect each other at the apex of said imaginary equilateral trigonal piramid and the units are disposed in the envelope of a cathode ray tube such that the shadow mask of a colour television receiving tube lies on the point of intersection.

The details of the construction of each electron gun unit are as follows: As shown in FIG. 1, the electron gun unit 1a, for example, includes a bottomed cylindrical first grid electrode 5a, and a bottomed cylindrical cathode electrode 7a which is concentric with said grid electrode 5a and contains a heater 6a. A thermionic electron emitting surface of the cathode electrode 7a is positioned at a predetermined distance from an electron emitting opening 8a of the first grid electrode 5a. The electron gun unit 1a further includes a coaxial second grid electrode 9a with its bottom spaced by a predetermined distance from the bottom of the first grid electrode 5a. On the axis of the second grid electrode 9a is provided an opening 100 for providing a passage for the electron beam. Similarly, a third, a fourth and a fifth grid electrode 14a, a and 16a respectively, are coaxially arranged in succession on the axis of the second grid electrode, said grid electrodes 14a, 15a and 16a having aligned openings 11a, 12a and 13a for passing the electron beam. On the opposite ends of the third grid electrode 14a are provided cylindrical projections 17a and 18a of a reduced diameter and having said openings 11a and 12a, respectively. The third grid electrode 14a is combined with the second and fourth grid electrodes 9a and 15a such that portions of the cylindrical projections 17a and 18a are partly received in the second and fourth grid electrodes, respectively. As shown in FIG. 1, the third grid electrode 14a can be readily fabricated by joining two cylindrical halves respectively having cylindrical projections 17a and 18a. Like the third grid electrode 14a, the fifth grid electrode 16a is formed with a. cylindrical projection 19a of reduced diameter having an opening 13a for the electron beam, projection 19a being partly received in one end of the fourth grid electrode 15a. The remaining electron gun units 1b and 1c are constructed identical to the electron gun unit In.

The electron gun structure constructed as above described is incorporated in the neck portion of a shadow mask type colour television cathode ray tube and an anode voltage is applied to the third grid electrodes 14a, 14b and 140 and to the fifth grid electrodes 16a, 16b and 160, whereas a voltage amounting to 5 to 20%, preferably from 15 to 20%, of the anode voltage is impressed upon the fourth grid electrodes 15a, 15b and 15c. For example, the anode voltage may be 20 kv., and a focussing voltage of 3360 to 4000 v. may be applied to the fourth grid electrodes. In this manner, voltages of appropriate values are applied to the third to fifth grid electrodes to form an electronic lens. Since portions of cylindrical projections of reduced diameter of the third and fifth grid electrodes are partially received in the fourth grid electrode, disturbance of the internal lens field caused by an external field invading through gaps which are present in conventional structures between the electrodes can be positively eliminated. For this reason, clear and sharp images can be reproduced especially in the shadow mask type colour television cathode ray tube.

The typical values of dimensions of electrodes and applied voltages for the electron gun unit 1a shown in FIG. 1 of the electron gun structure designed for use in a l9-inch colour television cathode ray tube are as follows: The internal diameter of the first grid electrode 5a- 10 mm.; the diameter of the opening 8a for passing the electron beam-0.58 mm.; the diameter of the opening 10a for passing the electron beam of the second grid electrode1.22 mm.; the gap between the second grid electrode 9a and the first grid electrode 5a0'.4i0.0l mm.; the diameter of openings 11a and 12a for passing the electron beam of the third grid electrode-1.9 mm.; the gap between the large diameter portion of the third grid trode 14a and the second grid electrode 9a3.25 mm.; the internal diameter of the fourth grid electrode 15a 10.1 mm.; the length of the portion of the projection 18a of the reduced diameter of the third grid electrode 14a received in the fourth grid electrode 15a1 mm.; the gap between the fifth grid electrode 16a and the third grid electrode 14a and the second grid electrode 9a3.25 mm.; for passing the electron beam-4 mm.; the length of the portion of the projection 19a of the reduced diameter and received in the fourth grid electrode 15a1 mm.; the internal diameter of the fifth grid electrode 16a--9.5O mm.; the outer diameter thereof-10 mm.; the distance between the axis of the three electron gun structure and the axis of 2a of the electron gun unit 1a-6.70i0.02 mm.; the angle between these axes-13'i5. A voltage of minus 100 volts was applied to the first grid electrode 5a, 200 volts to the second grid electrode 9a, the anode voltage of 23 kv. to the third grid electrode 14a and the fifth grid electrode 16a, and a voltage of from 1150 to 4600 v. to the fourth grid electrode 15a", and obtained satisfactory results.

FIG. 3 shows a voltage distribution along the axis of each electrode of the electron gun described above. As shown, the voltage of the third and fifth grid electrodes coincide with the anode voltage whereas the voltage of the fourth grid electrode is slightly less than the anode voltage.

FIG. 4 shows a comparison between the beam modulation characteristic A of a prior art electron gun of the bi-potential type and that B of the electron gun of this invention. Curve B shows that, with the electron gun of this invention, even when the modulation voltage varies greatly, the diameter of the beam spot is stable and is maintained small.

While the electron gun constructed as above described has the same number of electrodes as the conventional unipotential type electron gun, as the distance between the third and fifth grid electrodes is decreased, the overall length of the electron gun structure can be reduced. At the same time, the low voltage (0300 v.) focussing characteristic inherent to the conventional unipotential type electron gun can be eliminated, thus providing a new operating characteristic.

As above described, the focussing voltage amounts to about 20% of the anode voltage, so that it is possible to keep the potential difference between the third to fifth grid electrodes which form the main electronic lens less than that of the conventional low voltage unipotential type. More particularly, in the conventional low voltage unipotential type, the potential of the electron gun is equal to the difference between the anode voltage and substantially zero volts, or substantially equal to the anode voltage, whereas in the embodiment of this invention shown in FIG. 1 said difference equals to from to 83.2% of the anode voltage, or a reduction of about 20%. The anode voltage for large sized colour cathode ray tubes is generally more than 20 kv. For this reason, a three electron gun structure to be accommodated in the neck portion of a cathode ray tube having a diameter of 36 mm., for example, has a small inter-electrode gap so that it is extremely diflicult to eliminate the occurrence of sparks between electrodes. Reduction by 20% of the voltage difference between electrodes comprising the main electronic lens contributes to the improvement in maintaining stable operation.

Further, the electron gun illustrated is characterised by a long focal length with respect to the variation in the focussing voltage even when it is designed to operate at a higher focussing voltage, so that the requirement for maintaining the focussing voltage ratio at a prescribed value can be alleviated, thus enabling a simpler regulator circuit to be used.

Further, as the potential of the third grid is equal to the anode voltage, the potential at the point of beam intersection formed in front of the cathode electrode (that is the state wherein the electron beam emitted from the cathode electrode is preliminarily focussed by an electric lens formed by the first and second grids to form a beam of a minimum cross section) can be made about twice as high as that of the conventional bi-potential type. Since the diameter of this point of intersection is inversely proportional to the /2 power of the potential it is possible to reduce the diameter by about 30% 'when compared with the conventional type. Further, it becomes possible to focus the beam in front of the main focussing lens substantially independently of the focussing voltage thus enabling any desired diameter of the beam to be selected. Accordingly, by increasing the potential at the point of intersection, and by proper selection of the degree of focussing, it is possible to greatly improve the blooming characteristic wherein the beam spot size is increased by the beam modulation, thus improving the clearness and sharpness of the image with high brightness.

In this manner, while limiting the voltage between electrodes that comprise the main lens to a low value sufiicient to prevent undesirable sparks, a clear image of high brightness can be readily produced. Moreover, as the blooming characteristic is greatly improved, the electron gun can be applied to large sized cathode ray tubes with satisfactory results. In other words, there are provided colour cathode ray tubes capable of producing bright and sharp images and having stable operating characteristics.

FIGS. 5 and 6 illustrate a modified three electron gun structure embodying the above-described principles. In this embodiment since only the fifth grid electrode is different from the previous embodiment, corresponding parts are designated by the same reference numerals and their description is eliminated. The fifth grid electrode 16a of the electron gun unit 101, for example, shown in FIG. 5 takes the form of a bottomed cylinder having an outer diameter considerably smaller than the inner diameter of the fourth grid electrode a. The open end of the cylinder is slightly flared outwardly. The other two electron gun units 1b and 1c are constructed similar to unit 1a.

In the modification, since the fifth grid electrode 16a has a diameter smaller than that of the fifth grid electrode 16a in the previous embodiment, it is more difiicult for an electric discharge to occur between the fourth and fifth grid electrodes 15a and 16a. In the same manner, al-

though not shown in the drawing, the third grid electrode 14a can also be made to have an identical configuration as the fifth grid electrode 16a to increase a breakdown strength between electrodes.

FIGS. 7 to 13 illustrate one example of the apparatus of the present invention for assembling the three electron gun structure shown in FIG. 1. Referring first to FIG. 7, the apparatus comprises a pillar shaped supporting member 21 fixed to a base 20. As shown in FIG. 8, the supporting member 21 is provided in its periphery with three equally spaced V-shaped grooves 22 which are arranged such that the bottoms of these grooves lie on the apices of an equilateral triangle. In one groove 22 is inserted a reference pillar 23 on which are mounted respective electron gun electrodes 5a-16a constituting the electron gun unit 1a, for example, shown in FIG. 1. The reference pillar 23 includes an electrode supporting member 25 and a tapered portion 24 which is inclined at a pre determined angle 0 with respect to the axis of the electron gun structure. When the tapered portion 24 is received in one of the V-shaped grooves 22 the position of the axis 2a of the electron gun unit is automatically determined. As shown in FIG. 7, the reference pillar 21 supports coaxially various electrodes comprising the electron gun units and at predetermined spacings, the opposite ends of the pillar 21 being supported by an electron gun unit aligning a jig 26. More particularly, the jig 26 is in the form of a generally C shape and is formed at one end 27 with a projection 29 adapted to be received in a shallow opening 28 at the end of the tapered portion 24 of the reference pillar 23. On the other end of the jig 26 is provided an arm 39 having an opening 40 which slidably re ceives a holding rod 30 'which is slidable in the longitudinal direction of the jig and functions to support a rod 30 urged against the electrodes mounted upon the reference pillar 23 to form the electron gun unit 1a. The supporting rod 30 is surrounded by a helical spring 35 which compresses the electrode assembly in the axial direction, viz, in the direction of arrow D. An L-shaped groove 38 is formed through the peripheral wall of arm 39' to slidably receive a pin 39,, connected to the side of the supporting rod 30 to limit its sliding movement. Further an operating knob 36 is secured to the top of the supporting rod 30.

Normally, the supporting rod 30 is operated by the operating knob 36. Thus, sliding movement of the supporting rod 30 is stopped when pin 39, engages a horizontal portion 38 of the L-shaped groove 38. On the side wall of the jig 26 at an intermediate point between the ends thereof is secured a pressing member 37 which functions to urge the tapered portion 24 against the side wall of the groove 22 of the pillar shaped supporting member 21. A pair of first electrode holders 31 (FIG. 9) combined with electrodes through first spacers 32 and second spacers 32' are mounted in opposing relationship on the electrode supporting member 25 of the reference pillar 23, whereby the fourth grid electrode 15a is supported. There, are also provided a second holder 33 and a third holder 34 which are successively interposed on supporting member 25 with predetermined gaps therebetween. The manner of holding the fourth grid electrode 15a by the first electrode holder 31 composed of said first and second spacers will now be described in detail with reference to FIGS. 9 to 13.

As shown in FIG. 12, the opposite ends of the fourth grid electrode 15a comprising the main electronic lens are held by a pair of first and second spacers 32 and 32', shown in FIG. 9A and 9B with their inner surfaces engaged with holders 52 and 52 of the first spacers. First and second spacers 32 and 32' are superposed with respect to each other as shown in FIG. 12. Slots 54 and 54' (see FIGS. 11A and 11B) having a U-shaped section and provided at the centre of the first and second spacers 3'2 and 32' respectively receive reduced diameter portion 18a of the third grid electrode 14a and reduced diameter portion 19a of the fifth grid electrode 16a to maintain the third and fifth grid electrodes in a coaxial relationship. Second spacer 32 cooperates With first spacer 32 to maintain the desired spacing between electrodes. These spacers are split into two pieces so as to permit removal of the first spacer 32 from the fourth grid electrode 15a and to define a circular opening by means of U-shaped slots when said two pieces are rotated relative to each other. After assembled in this manner arms 55 of respective spacers 32 and 32' are rotated about the axis of the electron gun unit, as shown in FIG. 13. U-shaped slots 54 and 54 of second spacers which are angularly displaced by degrees, as shown in FIGS. 9B and 13, will define a circular opening when viewed in the axial direction Whereby the fourth grid electrode 15a will be brought into axial alignment with the third and fifth grid electrodes 14a and 16a.

FIGS. 10A, 10B, 11A and 11B show modified spacers. As can be noted from FIG. 12, when the thickness of the second spacers 32 is determined to a prescribed value the length B of reduced diameter portions of the third and fifth grid electrodes 14a and 16a that are received in the fourth grid electrode 15a can be predetermined to any desired length. Further by varying the thickness of two spacers, the spacing L between the third and fifth grid electrodes can also be varied to any desiredvalue.

A process of assembling the electron gun unit 1a by utilizing the apparatus described above will be described hereunder. First, as shown in FIG. 7, the fifth grid electrode 16a is mounted upon the electrode supporting member of reference pillar 23, then the second spacer 32 and the first spacer 32 shown in FIGS. 9A' and 9B are mounted on the fifth grid electrode with their U- shaped slots 54 and 54 fitted around the reduced diameter portion 19a of the fifth grid electrode 16a. Then one end of the fourth grid electrode 15a is fitted around the shoulder of the first spacer 32. In the same manner the other end of the fourth grid electrode 15a is fitted around the shoulder of the other first spacer 32 and a second spacer 32 is mounted on the first spacer. The second spacer 32 may be mounted simultaneously with or subsequently to the mounting of the third grid electrode 14a. Then the third grid electrode 14a is mounted upon the supporting member 25 to insert one of its reduced diameter portions into U-shaped slots 54 and 54' of the first and second spacers 32 and 32. Thereafter, the second holder 33 is mounted around the other reduced diameter portion of the third grid electrode 14a to engage the end surface of the large diameter portion thereof. Then the second grid electrode 9a, the third holder 34 and the first grid electrode 5a are successively mounted around the reduced diameter portion of the supporting member 25. Then the reference pillar 23 supporting respective electrodes, spacers and holders is mounted upon the electron gun unit aligning jig 26 to axially align various elements. More particularly, the operating knob 36 is manipulated to slide the rod under the biassing of the spring to cause the various electrodes to align. Then the first and second spacers 32 and 32' are rotated relative to each other to hold the fourth grid electrode in coaxial relationship with the other electrodes. After aligning the various elements in this manner, tapered portion 24 of the reference pillar 23 is inserted in one of the V-shaped grooves 22 of supporting member 21. The pillar 23 is maintained at an inclined position at 6 degrees with respect to the axis 50 of the electron gun structure by means of press member 37. Thereafter, respective electrodes are secured to insulating supporting rods 4a, 4b and 40 (see FIG. 2) and then holders and the first and second spacers are removed from the electrode assembly. In this case, the first spacer 32 is returned to the position at which the fourth grid electrode was originally mounted, and is then disengaged from the inner wall of the fourth grid electrode 15a after the removal of the second spacer 32'. While the above description refers to the electron gun unit 1a, the other units 1b and 1c are similarly assembled to complete a three electron gun structure.

With this apparatus, by using the first and second spacers constructed as above described it is possible to readily and correctly position the fourth grid electrode 15a in the exact coaxial relation with respect to the other electrodes. Thus, the first and second spacers are formed with U-shaped slots at different angular positions so that by relatively rotating these spacers it is possible to define a circular opening coaxial with other electrodes. Thus,

the fourth grid electrode received in said circular opening is automatically brought into coaxial relationship with the other electrodes.

The angle 0 between U-shaped slots of the first and second spacers may be any desired angle as long as the slots can define a circular opening by suitable combination of spacers shown in FIGS. 9A, 9B, 10A, 10B or 11A and 11B. If desired, more than two spacers may be used to define a circular opening.

FIG. 14 shows a side view, partly in section, of a modified apparatus for assembling a three electron gun structure shown in FIG. 5, for use in shadow mask type colour television receiving tubes. On the upper surface of a base are provided three equally spaced apart tapered openings 61 on a circle of radius R around the axis 50 of an assembled three electron gun structure, the axes of tapered openings 61 being on apices of an equilateral triangle. The axis of each tapered opening 61 has an angle of inclination 0 with respect to the axis of the electron gun structure and the angle 6 of the tapered opening 61 is selected to satisfy a relation 0 56 Tiltable outer pillars 63 are pivotally connected to the base at points 62 outside tapered openings 61.

On the upper end of each outside pillar 63 is driven a pin 64 having a tapered portion adapted to be received in a tapered opening 66 of a connected plate 65. The outside pillar 63 is secured in position by a lock nut 68 and a pin 67 laterally extending through pin 64 and lock nut 68. Each of the three tapered openings 61 of the base 60 accommodates a centre rod 69 (only one is shown) to provide the same axes 2a, 2b and 2c for respective electron gun units of the electron gun structure. At least one combination spacer 70, a reference element 71 and spacers 72, 73 and 74 defining the gaps between respective electrodes 5a, 9a, 14a, 15a and 16a are coaxially mounted on the centre rod 69. A clamping member 75 is fit within the first grid electrode 5a having a through opening 76 for accommodating the upper end of the centre rod 69 and an opening 77 used as a spring seat for receiving a helical spring 78.

As shown in FIG. 15, the centre rod 69 is formed as a stepped rod having coaxial cylindrical portions 80, 81. 82, 83 and 84 of different diameters and a tapered lower end 85. The tapered lower end has the same taper angle :9 as the tapered opening 61 so that they can snugly interfit. The cylindrical portion 80 has an end surface 86 adapted to support the combination spacer 70. The cylindrical portion 81 fits within the combination spacer 70 and the reference element 71 while the cylindrical portion 82 has a side surface slightly longer than the fifth grid electrode 16a and received therein and an end surface 88 adapted to engage the perforated inturned flange of the fifth grid electrode 16a. The cylindrical portion 83 extends through the third grid electrode 14a while the cylindrical portion 84 extends through the first and second grid electrodes 50: and 9a and the clamping member 75.

As best shown in FIG. 16 the reference member 71 takes the form of a hollow cylinder having a cavity 89 to coaxially receive the fifth grid electrode 16a. The reference member 71 is provided with two slits 90 spaced apart by in the circumferential direction to receive the supporting band 3 (see FIG. 14) of the fifth grid electrode 16a, a cylindrical portion 91 to accommodate the fourth grid electrode 15a, cylindrical portion 94 having end surfaces 92 and 93 respectively adapted to engage an end surface of the fourth grid electrode 15a and the combination ring spacer 71), said cylindrical portion 94 receiving the cylindrical portion of the centre rod 81.

With the modified assembling apparatus, the reference element 71 serves to coaxially insert the fourth grid electrode 15a, in the cylindrical portion 91 and further to coaxially accommodate the cylindrical portion 81 of the centre rod 69 so that the reference pillar 23 acts to align the fourth grid electrode on the same axis of other electrodes 5a, 9a, 14a, and 16a, mounted on the centre rod 69. The combination ring spacer 70 serves to determine the position of the third grid electrode 14a by the action of reference element 71, the fourth grid electrode 15a and spacer 72. The fifth grid electrode 16a is mounted on the cylindrical portion 82 of the centre rod 69 in such a manner that the perforated inturned flange of the elec trode 16a abuts against the end surface of the cylindrical portion 82 so that the spacing between the third and fifth electrodes may be adjusted to any desired value by selecting at least one of a plurality of combination ring spacers. The helical spring 78 applies the desired pressure to respective electrodes along the axis thereof via the plate 65. Outside pillars 63 serve to maintain the electrode assemblies in position which are assembled by means of centre rod 69 and reference element 71. Since the angle of inclination of the inner surface of the tapered opening 61 is related to the angle of inclination 0 of the centre rod 69 according to an equation 0 50 it is easy to smoothly remove from the base 60 the electron gun structure formed by assembling three electron gun units 1a, 1b and 1c in the manner described above, together with centre rod 69, reference element 71 and combination ring spacer 70. Furthermore, since the fifth grid electrode 16a is received in the cavity 89 of the reference element 71 and is fit over the cylindrical portion 82 of the centre rod 69, after the centre rod 69 has been removed from the assembled electron gun structure 1a the reference element 71 and the combination ring spacer 70 can be readily removed. The other two electron gun units 1b and 1c are assembled in the same manner.

-In order to assemble the three electron gun structure by using the above described assembling apparatus, three centre rods 69 each mounted with a desired combination ring spacer 70 and a reference element 71 are positioned in three tapered openings in the base 60. With particular reference to the electron gun unit 1a, for example, the fifth grid electrode 16a is mounted upon the centre rod 69 and the electrode 16a is inserted in the cavity 89 of the reference element 71 such that the supporting bands 3 attached to the electrode 16a will be received in slits 90 of the reference element 71 and that the perforated flange of the electrode 16a will engage the end surface 88 of the cylindrical portion 82 of the centre rod 69. Then, the fourth grid electrode 15a is fitted over the cylindrical portion 91 of the reference element 71 until one end of the electrode 15a comes toengage the end surface 92 of the cylindrical portion 94. Then the third and second grid electrodes 14a and 9a and the first grid electrode together with the helical spring 78 cooperating with clamping member 75 are successively mounted on the centre rod 69. In this case, suitable spacers 72, 73 and 74 are interposed between electrodes 15a, 140, 9a and 5a. Thereafter, supporting bands 3 attached to respective electrodes 5a, 9a, 14a, 15a and 16a are adjusted to lie in the same direction. Then, outside pillars 63 are rotated towards the electrode assemblies and fastened together by means of connecting plate 65,, lock nuts 68 and cross pins 67. Then, the supporting bands 3 attached to respective electrodes 15a, 14a, 9a and 5a are se cured, as by fusion, to glass supporting rods 4a, 4b and 40 (see FIG. 6) located between adjacent electron gun units 1a, 1b and 1c, thus completing the electron gun structure.

To remove the completed electron gun structure from the assembling apparatus, lock nuts 68 and connecting plate 65 are removed from pins 64. Then outside supporting pillars 63 are rotated outwardly away from the electrode assembly and the electron gun structure assembled into a unitary structure by being secured to the supporting rods is removed from the base 60 together with the associated centre rod 69, reference element 71, combination ring spacer 70, spacers 72, 73 and 74, clamping member 75 and helical spring 78. Because of the taper fit between the lower ends of the centre rods 69 and the tapered openings 61, the centre rods can be readily withdrawn from tapered openings 61. Then, the centre rod 69, reference element 71, combination ring spacer 70, spacers 72, 73 and 74, clamping member 75 and helical spring 78 are removed from each one of electron gun units 1a, 1b and 1c to leave a completed electron gun structure.

The invention is also applicable to the fabrication of two electron gun structures utilised in cathode ray tubes for observation purposes.

In a two electron gun structure, two electron gun units are disposed symmetrically with respect to the axis of the structure at a predetermined angle of inclination.

Accordingly, such an electron gun structure can be assembled in the following manner. Thus two tapered openings are provided for respective electron gun units at positions symmetrical to the axis of the base of the assembling apparatus. In the same manner as for the above described apparatus for assembling three electron gun structures, outside pillars, a plate for connecting outside pillars, centre rods for coaxially aligning respective electrodes, reference elements, helical springs, combination ring spacers for adjusting the gap between the third and fifth grid electrodes and spacers to adjust the spacing between other electrodes are also provided. With this assembling apparatus, two electron gun structures can also be readily assembled in the same manner as three electron gun structures.

Although, in the above embodiment, the reference element 71 was directly fitted over the centre rod 69, as shown in FIG. 17 the reference element 71 may be received in a recess formed on the upper surface of the base 60 coaxially with the tapered opening 61. Alternatively, a rib (not shown) may be substituted for the recess 95 for mounting the reference element 71 coaxially With the centre rod 69.

Further, in the above described embodiment, the combination ring spacer 70 was shown to abut against the end surface 93 of the reference element 71, the combination ring spacer 70 may fit on the cylindrical portion 91 of the reference element 71.

Further, a helical spring may be formed from a Wire or strip, the latter being preferred because it does not band laterally, but applies pressure mainly in the longitudinal direction.

What we claim is:

1. An apparatus for assembling a multiple element type electron gun structure, said gun structure including:

a plurality of unitary bonded electron gun units, each of said electron gun units comprising a cathode electrode emitting an electron beam, first and second grid electrodes controlling said electron beam, and third, fourth and fifth grid electrodes forming a lens system which effects focussing of said electron beam, said fourth and fifth grid electrodes having a substantially cylindrical cross-section, said third and fifth grid elec trodes each being provided with a substantially cylindrical projection having a diameter smaller than the inner diameter of said fourth grid electrode on at least one side thereof opposing said fourth grid electrode so that at least a portion of each of said projections is received in said fourth grid electrode; and

said assembling apparatus comprising:

first and second holders, each including a first spacer adapted to fit around one of the corresponding cylin drical projections of said third and fifth grid electrodes, said first spacer including a slot having a curved portion of the same configuration as the outer periphery of said cylindrical projection; a second spacer including a slot similar to said slot of said first spacer but provided at a different angular position and a circular shoulder adapted to fit within one end of said cylindrical fourth grid electrode having the inner diameter larger than the outer diameter of said projection, said second spacer being mounted adjacent said first spacer to receive said projection;

a centre rod including a first cylindrical portion received in said fifth grid electrode, said first cylindrical portion having substantially the same configuration as said fifth grid electrode, one end of said first cylindrical portion extending through an opening for the electron beam of said fifth grid electrode, a second cylindrical portion contiguous to said first cylindrical portion and extending through two openings for the electron beam provided on both ends of said third grid electrode, and a third cylindrical portion contiguous to said second cylindrical portion to successively extend through openings for the electron beam of said second and first grid electrodes; a third holder interposed between said third and second grid electrodes; a fourth holder interposed between said second and first grid electrodes; means to apply a compressive force along the longitudinal direction of said centre rod to cause all of said spacers and grid electrodes to intimately contact each other; means to support said centre rod on a base at a predetermined angle of inclination; and means to integrally bond each of said electrodes to glass supporting rods through supporting bands.

2. An assembling apparatus according to claim 1 wherein said first cylindrical portion to be received in said fifth grid electrode includes a reference portion contiguous to the lower end thereof, and wherein said means for supporting said centre rod comprises a pillar shaped supporting member fixed to said base and having a groove of V-shaped cross section, said reference portion being held against side walls of said groove, a supporting rod with one end thereof received in said first grid electrode and an electron gun unit aligning jig, one end of said jig supporting said holding rod while the other end of said jig holding the lower end of said centre rod.

3. An assembling apparatus according to claim 1 wherein said means for applying pressure comprises a perforation formed on one end of said electron gun unit aligning jig and adapted to support said holding rod free to slide in the axial direction of said centre rod, an L-shaped groove formed on said one end of said jig, a pin secured to said holding rod to be slidable in said slot, and a helical spring surrounding said holding rod to apply pressure to said holding rod towards said first grid electrode, said helical spring being interposed between said jig and said holding rod.

4. An apparatus for assembling a multiple element type electron gun structure, said gun structure including:

a plurality of unitary bonded electron gun units, each of said electron gun units comprising a cathode electrode emitting an electron beam, first and second grid electrodes controlling said electron beam, and third, fourth and fifth grid electrodes forming a lens system which effects focussing of said electron beam, said fourth and fifth grid electrodes having a substantially cylindrical cross-section, said third and fifth grid electrodes each being provided with a substantially cylindrical projection having a diameter smaller than the inner diameter of said fourth grid electrode on at least one side thereof opposing said fourth grid electrode so that at least a portion of each of said projections is received in said fourth grid electrode; and said assembling apparatus comprising:

a base having a plurality of tapered openings of the number corresponding to that of the electron gun units to be assembled; a centre rod including a tapered portion received in one of said tapered openings, a first cylindrical portion extending through said fifth cylindrical grid electrode and having a shoulder to engage an opening for the electron beam of said fifth grid electrode, a second cylindrical portion contiguous to said first cylindrical portion and extending through two openings for the electron beam of said third electrode, and a third cylindrical portion contiguous to said second cylindrical portion and extending successively through openings for the electron beam of said second and first grid electrodes; a reference element coaxial with said first cylindrical portion and located on the outside thereof, said reference element having a shoulder to be received in said fourth grid electrode; a combination ring spacer to be inserted beneath said reference element; a first spacer interposed between said third and fourth grid electrodes; a second spacer interposed between said third and second grid electrodes; a third spacer interposed between said second and first grid electrodes; means to apply pressure from said first grid electrode towards said base along the axis of said centre rod; and means to integrally bond said electrodes to glass supporting rods through supporting bands.

5. An assembling apparatus according to claim 4 wherein said means for applying pressure comprises outer supporting pillars with one end pivotally connected to said base, pins secured to the other ends of said outer supporting pillars, a connecting plate having tapered openings to receive said pins, a clamping member inserted in the open end of said first grid electrode, said clamping member having a through opening to receive one end of said third cylindrical portion of said centre rod and a spring seat, and a helical spring made of a spring strip and interposed between said spring seat and said connecting plate to urge said clamping member towards said base.

6. An assembling apparatus according to claim 4 wherein said reference member includes slits for receiving the supporting band of said fifth grid electrode, said slits being spaced apart in the circumferential direction.

7. An assembling apparatus according to claim 4 wherein the angle of inclination of said tapered portion of said centre rod is smaller than that of the tapered opening in said base.

8. An assembling apparatus according to claim 4 wherein said base is provided with a recess concentric with said tapered opening and said ring spacer and said reference elements are received in said recess.

References Cited UNITED STATES PATENTS 3,340,035 9/1967 Hajduk 65154 3,434,819 3/1969 Merchant et al 65155 ARTHUR D. KELLOGG, Primary Examiner US. Cl. X.R.

65-154; 3l3--69C, 70C 

